[Travis McGee]

That Webster quote doesn’t ring true to the era. Do you have attribution?

[DuncanWaring]

Looking into it a little more rigorously makes it look like that particular phrasing may be a fabrication. However, I've found a book titled the "Illustrated Fryeberg Webster Memorial ", Page 14 contains the passage

...Miracles do not cluster. That which has happened but once in six thousand years cannot be expected to happen often. Such a government, once gone, might leave a void, to be filled, for ages, with revolution and tumult, riot and despotism.

I can't get a usable URL to get directly to it, but if you go to books.google.com and search on "Illustrated Fryeburg Webster Memorial" it'll get you a scanned image version of the book (apparently published in 1882).

[DuncanWaring]

A further search on the phrase "miracles do not cluster" at books.google.com produces a claim that statement was in a Fourth of July speech delivered in 1802.

Turning on the Light, Horatio King, 1895.